The present invention relates to the provision of distinctive marking in the directions of travel on motoring highways, airports and other surfaces with the aid of thin marker strips adhered to the traveling or other surfaces, and employing successively spaced wedges provided sometimes with retro-reflective materials and other times with only diffusely reflecting surfaces; the invention being more particularly concerned with improved marker strips for such and related purposes.
In my earlier U.S. Letters Patent No. 4,681,401 issued on July 21, 1987, an effective improved thin surface marking strip for adhering to a road surface or the like is disclosed embodying novel somewhat flattened, wedges having retroflective material and of preferably substantially trapezoidal shape in longitudinal vertical section (longitudinally of the strip) with rather critical separations between the wedges relative to height and width of the wedges to obviate shadowing effects, as in sunlight, to provide improved daylight observation, and to increase effectiveness and life, particularly under conditions of rain-covered surfaces and snow. Earlier art dealing with this type of technology is disclosed in U.S. Letters Patent Nos. 4,236,788; 4,069,787; 4,040,760 and 3,920,346.
While the marker strips of my earlier U.S. Pat. No. 4,681,401 have been particularly promising, certain difficulties have been encountered in testing under the more strenuous conditions of use, including heavy rainfall and heavy snow, and the practical considerations of the use of heavy vehicle traffic and of snow removal plows and similar implementations in the colder climates. In particular, it has been found that the necessary spacing between successive transverse wedges having retro-reflective material on the inclined trapezoidal front and leading surfaces of the wedges in order to prevent the obscuring of the strips by the shadows that they cast in sunlight, have had some practical problems in some instances with the snowplow blades catching in the horizontal longitudinally extending spaces between the wedges, which introduces wear and damage problems that were not anticipated. In addition, the severe use of the device, particularly after wear, has been found to reduce the effectiveness of visibility under wet conditions, which has given rise to a further feature of the present invention in terms of rather critical height dimensions to the wedges.